Frozen confections which contain a hydrate of a gas such as carbon dioxide (CO2) or nitrous oxide (N2O) give a pleasant sparkling or fizzy sensation when consumed. Such products are disclosed for example in WO 94/02414, WO 97/16980 and U.S. Pat. No. 4,398,394. Gas hydrates (also known as clathrates) are usually produced by contacting the gas with water under high pressure and then reducing the temperature. Generally, an excess of water is used so that a composite consisting of gas hydrate crystals in ice is formed. The composite is then typically ground into particles and mixed with the other ingredients of the frozen confection (e.g. a syrup or mix containing sugar, flavour, protein, fat etc.). The gas hydrate is formed using essentially pure water, since the presence of other ingredients (such as sugar, colour, flavour etc.) decreases the controllability of the process and/or reduces the stability of the product.
WO 02/34065 discloses a method for preparing a carbonated beverage wherein carbon dioxide hydrate particles are mixed with a syrup component. It is stated that syrups which contain sugar should not be added before completion of the CO2-hydrate reaction because this makes the reaction less stable as the syrups tend to foam. When an artificially sweetened syrup is used, it can be added before the hydrate is formed. When such a syrup is used pectin and guar gum can be added into the product during mixing to prevent separation. There is no suggestion that any other substances could be added before the hydrate is formed.
U.S. Pat. No. 5,538,745 discloses a process for producing frozen confections by mixing particles of sugar encapsulated in fat into a frozen aerated solution of milk protein. It is stated that clathrate ice crystals can be formed by adding CO2, N2, N2O or mixtures thereof to the protein solution. These gases can comprise up to 100% of the gases used to aerate the solution. The milk protein is present in amounts typical for ice cream, i.e. >5 wt %.
The “activity” of the gas hydrate, i.e. the amount of entrapped gas per unit weight of ice, depends on temperature and pressure conditions in which the gas hydrate is produced as well as the relative amounts of gas and water that are contacted with each other.
It is desirable to be able to produce gas hydrates with increased activity and our co-pending application WO 2010/069770 discloses that composites of gas hydrate and ice having increased activity can be produced provided that an aerating agent is present during the formation of the gas hydrate. Although WO 2010/069770 provides gas hydrates with increased activity, alternative approaches are also highly desirable.